Clip-on sunglasses are designed to be removably attached to eyeglasses. For example, a person may have a pair of eyeglasses with un-tinted, prescription lenses. Clip-on sunglasses having tinted lenses may then be attached to the eyeglasses such that the person sees through both sets of lenses. As a result, the person obtains the benefit of the prescription lenses of the eyeglasses as well as the tinted lenses of the clip-on sunglasses.
It is desirable for the clip-on sunglasses to be quickly and easily attached and removed from the eyeglasses so that the person can selectively employ the clip-on sunglasses when desired. For example, the person may attach the clip-on sunglasses when going outdoors during the day and may remove them when returning indoors or upon nightfall.
There are number of devices that have been used to attach clip-on sunglasses to eyeglasses. For example, magnets have been employed in clip-on sunglasses to magnetically attach the clip-on sunglasses to eyeglasses having a ferrous metallic frame. Another example is a spring mechanism including a coiled metallic spring and in which frame parts having prongs at their outer portions are biased toward each other by the spring mechanism. The frame can be expanded by pulling the frame parts away from each other and, then, the frame can be placed over a pair of eyeglasses. When released, the spring secures the clip-on sunglasses to the eyeglasses by holding the prongs against outer edges of the eyeglasses. Another example is a clip-on sunglass in which its entire frame, including prongs, is molded of a single piece of hard plastic. The plastic of the frame is sufficiently resilient that the frame can be distorted such that the prongs can be slipped over the edges of the eyeglass frame and held in place.